Accumulation of selenium in mixotrophic culture of Spirulina platensis on glucose

Accumulation of Se in mixotrophic culture of Spirulina platensis was investigated in this study. Results indicated that glucose was better than acetate as an organic carbon source for mixotrophic culture of S. platensis. Supplementation of glucose (2 gL(-1)) significantly enhanced the biomass concentration (2.57 gL(-1)) and the production of phycocyanin (0.279 gL(-1)) and allophycocyanin (0.126 gL(-1)) in S. platensis, which were much higher than those of photoautotrophic culture (1.08 gL(-1), 0.119 gL(-1) and 0.042 gL(-1), respectively). Stepwise addition of Se during the growth phase avoided the inhibitory effect of high Se concentration on the growth of S. platensis. The Se enrichment favored the production of phycocyanin and allophycocyanin in the algal cells. The highest Se yield (1033 microgL(-1)) was obtained at an accumulative Se concentration of 250 mgL(-1), with organic Se percentage, biomass concentration, phycocyanin and allophycocyanin yields of 92.3%, 2.55 gL(-1), 0.295 gL(-1) and 0.153 gL(-1), respectively. These results indicated that the application of mixotrophic culture S. platensis with stepwise addition of Se to the medium could offer an effective and economical way for the production of high Se-enriched algal products.     

Kinetic models for phycocyanin production by high cell density mixotrophic culture of the microalga Spirulina platensis

Phycocyanin production by high cell density cultivation of Spirulina platensis in batch and fed-batch modes in 3.7-L bioreactors with a programmed stepwise increase in light intensity program was investigated. The results showed that the cell density in fed-batch culture (10.2 g L⁻¹) was 4.29-fold that in batch culture (2.38 g L⁻¹), and the total phycocyanin production in the fed-batch culture (0.795 g L⁻¹) was 3.05-fold that in the batch culture (0.261 g L⁻¹). An unstructured kinetic model to describe the microalga culture system including cell growth, phycocyanin formation, as well as glucose consumption was proposed. The data fitted the models well (r ² > 0.99). Furthermore, based on the kinetic models, the potential effects of light limitation and photoinhibition on cell growth and phycocyanin formation can be examined in depth. The models demonstrated that the optimal light intensity for mixotrophic growth of Spirulina platensis in batch or fed-batch cultures using a 3.7-L bioreactor was 80160 μE m⁻² s⁻¹, and the stepwise increase in light intensity can be replaced by a constant light intensity mode. Received 28 July 1998/ Accepted in revised form 8 October 1998     

The ultrastructure of Spirulina platensis in relation to temperature and light intensity

The ultrastructure of Spirulina platensis, a cyanobacterium with a helical morphology, has been studied in relation to temperature and light intensity. An increase in temperature gives rise to a more tightly coiled trichome, an increase in sheath material formation and a decrease in cyanophycin (above 17°C) and polyglucan (above 20°C) granule concentration. An increase in light intensity leads to an increase in gas vesicle concentration while the phycobilisome content decreases. Furthermore, cylindrical bodies have been observed with a somewhat different ultrastructure from those found in other species of cyanobacteria. The occurrence, size and ultrastructure of polyhedral bodies, photosynthetic lamellae, mesosomes, lipid deposits and an unknown kidney-shaped inclusion in relation to temperature and light intensity are described.     

Effects of phosphorus concentration and light intensity on the biomass composition of Arthrospira (Spirulina) platensis

This paper presents the effects of various phosphorus concentrations (10, 50, 250 and 500 mg l(-1) K(2)HPO(4)) on the biomass production and composition of Arthrospira (Spirulina) platensis in relation to light intensity (24, 42 and 60 μE m(-2) s(-1)). The maximum biomass production was 3,592 ± 392 mg l(-1) and this was observed in 250 mg l(-1) K(2)HPO(4) at 60 μE m(-2) s(-1) light intensity after 32 days of cultivation. A maximum specific growth rate (μ(max)) of 0.55 d(-1) was obtained in 500 mg l(-1) K(2)HPO(4) at 60 μE m(-2) s(-1). The protein, lipid and chlorophyll contents of the biomass varied from 33.59 to 60.57 %, 5.34 to 13.33 % and 0.78 to 2.00 %, respectively. The most significant finding was that phosphorus limitation (10 mg l(-1) K(2)HPO(4)) caused a drastic increase of the carbohydrate content (59.64 %). The effect of phosphorus limitation on the carbohydrate content was independent of the light intensity. The accumulated carbohydrates are proposed to be used as substrate for biofuel generation via one of the appropriate biomass energy conversion technologies. Also, it was observed that phosphorus removal is a function of biomass density, phosphorus concentration and light intensity.     

螺旋藻在光胁迫时的抗逆性研究

螺旋藻对于环境的变化有很强的适应性.以钝顶螺旋藻为实验材料,测定螺旋藻在受到较强光照胁迫时藻体的电导率以及脯氨酸、丙二醛和过氧化氢酶系的含量.在3000 lx光照下,螺旋藻6个藻株的电导率以及脯氨酸、丙二醛和过氧化氢酶系的含量比在1000 lx光照下明显升高,螺旋藻的电导率最高上升了2～6倍;细胞内的脯氨酸含量最多增加5倍,最少增加13%;丙二醛的含量增加40%～100%;过氧化氢酶的含量上升范围在19%～80%,过氧化物酶的含量上升范围在20%～100%.说明螺旋藻在受到光胁迫时自身会启动相关保护机制,产生一定的抗逆性,以适应环境的变化.     

Ecophysiological studies on Spirulina platensis Effect of temperature,light intensity and nitrate concentration on growth and ultrastructure

The ultrastructure of the cyanobacterium Spirulina platensis was studied in relation to temperature, light intensity and nitrate concentration. The organism was able to grow in media supplied with nitrate in concentrations up to 250mm. High nitrate concentrations increased the yield and growth rate at temperatures above 35°C. Occurrence, distribution and abundance of cyanophycin granules, polyglucan granules, cylindrical bodies, carboxysomes and mesosomes varied widely in relation to the factors studied. At low temperatures (up to 17°C) cyanophycin was the abundant organelle, especially at high nitrate concentrations, whereas in the temperature range 17–20°C polyglucan was found in large quantities particularly at low nitrate concentrations. Special attention was paid to the cylindrical bodies, the ultrastructure of which was dependent on temperature. Three types of ultrastructure were distinguished each with several possible shapes.     

Effects of light intensity and quality on the growth rate and photosynthetic pigment content of Spirulina platensis

The quantitative and qualitative effects of light on carotenoid production by Spirulina were studied. Maximum total carotenoid production was measured in cells grown under white light at an irradiance of 432 μmol photon m^?2 s^?1, the onset of light saturation for this organism as determined by growth rates. A true maximum may exist at irradiances above 1500 μmol photon m^?2 s^?1 under white light. Individual carotenoids responded differently to light conditions. Under white light, β-carotene and echinenone were most abundant at the lowest and highest irradiance levels tested. Myxoxanthophyll and lutein/zeaxanthin did not change over the same irradiance range. Under red and blue light, we found decreased values of myxoxanthophyll, while β-carotene increased and lutein/zeaxanthin and echinenone showed little change. In general, maximum carotenoid production requires optimization of the culture conditions that favor growth.     

Influence of ammonium chloride feeding time and light intensity on the cultivation of Spirulina (Arthrospira) platensis

This study dealt with the influence of both the feeding time and light intensity on the fed-batch culture of the cyanobacterium Spirulina (Arthrospira) platensis using ammonium chloride as a nitrogen source. For this purpose, a 2(2) plus star central composite experimental design combined with response surface methodology was employed, and the maximum cell concentration (X(m)), the cell productivity (P(X)), and the yield of biomass on nitrogen (Y(X/N)) were selected as the response variables. The optimum values of X(m) (1,833 mg L(-1)) and Y(X/N) (5.9 g g(-1)) estimated by the model at light intensity of 13 klux and feeding time of 17.2 days were very close to those obtained experimentally under these conditions (X(m) = 1,771 +/- 41 mg L(-1); Y(X/N) = 5.7 +/- 0.17 g g(-1)). The cell productivity was a decreasing function of the ammonium chloride feeding time and a quadratic function of the light intensity. The protein and lipid contents of dry biomass collected at the end of cultivations were shown to decrease with increasing light intensity.     

Growth and phycocyanin formation of Spirulina platensis in photoheterotrophic culture

Summary Glucose and acetate enhanced cell growth and phycocyanin production of S. platensis. The highest specific growth rate, cell concentration and phycocyanin production were respectively 0.62 d^-1, 2.66 g/l and 322 mg/l on glucose and 0.52 d^-1, 1.81 g/l and 246 mg/l on acetate. The specific growth rate of the alga on 2.5 g glucose/l was markedly increased with increasing light intensity up to 2 klux. Further increasing light intensity to 4 klux only resulted in a very slight increase in specific growth rate. At a light intensity above 4 klux, photoinhibition occurred. Light favoured phycocyanin formation. The highest phycocyanin content was obtained at a light intensity of 4 klux. When the light intensity decreased to 2 klux or less, the optimal glucose concentration for biomass production shifted from 2.5 g/l to 5.0 g/l.     

Kinetics and dynamics for light state transition in cyanobacterium Spirulina platensis cells

Light state transition in oxygenic organisms was defined as the ability to equalize the excitation of the two photosystems for maximal photosynthetic efficiency. In cyanobacteria, extensive researches on state transition have continuously provided new knowledge in the past decades but the molecular mechanism and physiological significance are still ambiguous. In this work, kinetics and dynamics of the transition from state 1 to state 2 in cyanobacterium Spirulina platensis cells were studied at different intensity of orange light from 10 to 120 μmol m(-2) s(-1). It was revealed that the state transition worked constantly independent of light intensity while the rates varied. The synchronous fluorescence kinetics for phycobilisome (PBS) and photosystem components indicated that the state transition was entirely regulated by "mobile PBS", and continuously changed fluorescence amplitudes suggested a series of intermediate states were involved between state 1 and state 2. The dynamic property of PBS movement during the state transition was revealed by (1,0) distribution of photo-linkable PBSs, indicating a collective movement of all PBSs. The results suggest that state transition in cyanobacteria possesses not only physiological but also photochemical significance.     

Scale-up and design of a pilot-plant photobioreactor for the continuous culture of Spirulina platensis

Scale-up of bioreactors has the intrinsic difficulty of establishing a reliable relationship among physical parameters involved in the design of the new bioreactor and the physiology of the cultured cells. This is more critical in those cases where a more complex operation of the bioreactor is needed, such as in photobioreactors. A key issue in the operation of photobioreactors is establishing a quantification for the interaction between external illumination, internal light distribution and cell growth. In this paper an approach to the scale-up of a photobioreactor for the culture of Spirulina platensis, based on a mathematical model describing this interaction, and the operation of a previous reactor 10 times smaller is presented. The paper describes the approach followed in the scale-up, the analysis of different design constraints, the physical realization of the new bioreactor design, innovative use of plastic material walls to improve reactor safety, and finally the corroboration of its satisfactory operation.     

Intracellular phosphorus pool in a culture of the cyanobacterium Spirulina platensis

An intracellular phosphorus pool in a monoculture of the cyanobacterium Spirulina platensis was assessed using radioactive and nonradioactive phosphorus. The derived dependence of specific growth rate on the intracellular content of mineral phosphorus can be presented in the form of the Droop equation. It was found that the stage of replenishment of the intracellular phosphorus pool may affect the phosphorus turnover estimation in aquatic environments from the results of short-term measurements of phosphorus uptake.     

Harvesting of Spirulina platensis by cellular flotation and growth stage determination

AIM: To investigate an effective harvesting method for Spirulina platensis. METHODS AND RESULTS: Eighty per cent of S. platensis cells in the logarithmic growth phase were harvested by flotation when the cells were set in a static condition for 2 h. The optimum harvesting time was about day 6 of cultivation. The flotation activity of S. platensis cells was enhanced by the addition of NaCl. CONCLUSIONS: The harvesting of S. platensis by flotation is a cost-effective and straightforward method that can retain the algal quality. The optimum harvesting time of S. platensis can be predicted by the cellular protein to carbon ratio. SIGNIFICANCE AND IMPACT OF THE STUDY: Flotation harvesting is also applicable to other cyanobacteria with gas vesicles.     

Effects of light intensity and dilution rate on the semicontinuous cultivation of Arthrospira (Spirulina) platensis. A kinetic Monod-type approach

Semicontinuous cultures were carried out at different dilution rates (D) and light intensities (I) to determine the maximum productivity of Arthrospira platensis cultivated in helicoidal photobioreactor up to the achievement of pseudo-steady-state conditions. At I=108 μmol photons m(-2) s(-1), the semicontinuous regime ensured the highest values of maximum cell concentration (X(m)=5772±113 mg L(-1)) and productivity (P(XS)=1319±25 mg L(-1) d(-1)) at the lowest (D=0.1 day(-1)) and the highest (D=0.3 day(-1)) dilution rates, respectively. A kinetic model derived from that of Monod was proposed to determine the relationship between the product of light intensity to dilution rate (ID) and the cell productivity, which were shown to exert a combined influence on this parameter. This result put into evidence that pseudo-steady-state conditions could be modified according to circumstances, conveniently varying one or other of the two independent variables.     

Role of light in the response of PSII photochemistry to salt stress in the cyanobacterium Spirulina platensis

The role of light in the effect of salt stress on PSII photochemistry in the cyanobacterium Spirulina platensis grown at 50 micromol m(-2) s(-1) was investigated. The time-course of changes in PSII photochemistry in response to high salinity (0.8 M NaCl) incubated in the dark and at 30, 50 and 100 micromol m(-2) s(-1) was composed of two phases. The first phase, which was independent of light, was characterized by a rapid decrease (20-50%) in the maximal efficiency of PSII photochemistry (F:(v)/F:(m)), the efficiency of excitation energy capture by open PSII reaction centres (F(1)(v)/F(1)(m)), photochemical quenching (q(P)), and the quantum yield of PSII electron transport (Phi(PSII)) in the first 15 min, followed by a recovery of up to about 86-92% of their initial levels after 4 h of incubation. The second phase took place after 4 h, in which a further decline in the above parameters occurred only in the light but not in the dark, reaching levels as low as 32-56% of their initial levels after 12 h. Moreover, the higher incubation light intensity, the greater the decrease in the above parameters. At the same time, Q(B)-non-reducing PSII reaction centres increased significantly in the first 15 min and then recovered to the initial level during the first phase, but increased again in the light in the second phase. Photosynthetic oxygen evolution activity decreased sharply by 70% in the first 5 min, and then kept largely constant until 12 h. The changes in oxygen evolution activity were independent of light intensity during both phases.     

Clarification and concentration with membrane technology of a phycocyanin solution extracted from Spirulina platensis

Membrane technologies were investigated with the aim to improve stability of C-Phycocyanin extracts resulting from ultrasonic breakage of Spirulina platensis. Five membranes, ranging from microfiltration to reverse osmosis, were utilized both for clarification and concentration steps. Nanofiltration with tubular organic membranes exhibited good performances: pigment recovery was 100%, mean permeation flux was 85 l h^–1 m^–2 for achieving a concentration factor of 7 with 30×10⁵ Pa pressure and 1.5 m s^–1 tangential velocity (turbulent flow).     

响应面分析法用于微生物培养基浓度的优化

首次将响应面分析法 (RSM )用于延胡索酸酶产生菌产氨短杆菌MA 2和黄色短杆菌MA 3培养基成份的优选 ,并且取得了良好的结果。经优化后产氨短杆菌MA 2酶活达 2 7.88×10 3 μmol/g·h ,黄色短杆菌MA 3酶活达 32 .2 6× 10 3 μmol/g·h ,较国内外文献报道的其它产氨短杆菌、黄色短杆菌单位菌体延胡索酸酶活力有显著提高。     

Fractionation and purification of the phycobiliproteins from Spirulina platensis

C-Phycocyanin and allophycocyanin of Spirulina platensis are fractionated and purified using a non-chromatographic method namely, aqueous two phase extraction for the first time. Optimized process parameters of aqueous two phase extraction (PEG 4000/potassium phosphate of tie line length 18.64% with a phase volume ratio 1.45) resulted in pure C-phycocyanin and allophycocyanin with a purity of 3.23 and 0.74, respectively, in a single extraction. Multiple extractions (two) improved the purity of C-phycocyanin from 3.23 to 4.02. Integration of aqueous two phase extraction with membrane process not only facilitated the separation of phase forming components from the products and also increased the purity of allophycocyanin from 0.74 to 1.5.